Question

If the ratio of concentration of electrons to that of holes in a semiconductors is $\frac{7}{5}$ and the ratio of currents is $\frac{7}{4}$, what is the ratio of their drift velocities?

• A. $\frac{4}{7}$
• B. $\frac{5}{8}$
• C. $\frac{4}{5}$
• D. $\frac{5}{4}$

Answer 1

The correct option is D

$\frac{5}{4}$

Given that, $\frac{n_e}{n_h}=\frac{7}{5}$ and $\frac{I_e}{I_h}=\frac{7}{4}$
Now, $\frac{(v_d{)}_e}{(v_d{)}_n}=\frac{I_e}{I_h}\times \frac{n_h}{n_e}=\frac{7}{4}\times \frac{5}{7}=\frac{5}{4}$